Replace Complete AC system 1990 Toyota SR5

[jiju1943]

I took a fellows word that installing the 134 in a R12 system would work, it did for a while, now nothing, the compressor won’t even click. My truck is a 1990 Toyota SR5 4X4 with the 6 cylinder. What parts will I need to completely replace everything, or is there a way to save any of the parts.

Topic

[Bluesnut]

The fact that the compressor doesn’t engage, etc does not mean you need to replace everything. It’s an aged system that probably has a few leaks and the compressor is not engaging due to low refrigerant. The usual leak source is the compressor seals.

A leak test could be done and this is best done with an electronic sniffer although often an oily blotch on the compressor or an A/C line means there is a leak in that area.
If the compressor is leaking and considering the age of the car it would be best to replace the compressor and the drier. You would need a set of gauges, vacuum pump, and preferably flush the system before installing the new parts.

There’s also the issue of expertise involved with repairing A/C and the potential dangers to a DIYer.

[Lorrin Barth]

Yeah, find the leaks, all of the leaks. That mean sniffing the condenser, evaporator, compressor and lines. On a vehicle that old any or all could be leaking. At least then you will have some idea of the cost.

[jiju1943]

Thanks fellows, I appreciate your help. I am an ole time mechanic but AC was not one of my strong points, I even went to AC school for autos but a lot has changed since then. LOL. The valve covers are leaking also so that would be a good time to take care of that also. Thanks again.

Jim

[Nick Warner]

Haven’t seen a lot of success with retrofits from R12. A lot of it has to do with the chemistry of the two. R-134a has smaller molecules than R-12 and the hoses originally made for R-12 are not molecular barrier hoses. You can literally leak refrigerant right through the hoses. Also, R-12 is a more efficient refrigerant than R-134a. It has a lower boiling point and can be cycled less often and at lower operating pressures. To achieve the same effect with R-134a requires a higher operating pressure and more frequent on time for the compressor. On an aged R-12 system they were not made to tolerate this.

The oils used in the two are also not compatible and when retrofitting a complete flush needs to be done to remove all the traces of the ester oil (mineral base) and be able to run PAG (synthetic). Not all the older compressor seals were made of a material compatible with a synthetic fluid and will begin to leak just from that.

If you need a compressor DO NOT buy a reman. Get a brand new one and not a China cheapie either.Trust me, they have a very high failure rate and when they grenade they will contaminate the whole system. You aren’t saving anything. What parts you do get need to be rated for R-134a. I’m not sure if the same body style as you have ran 134 in later years, in which case you could simply order the parts for that. The hoses must be a molecular barrier hose like a Gates PolarCool or equivalent.

[jiju1943]

Thanks nick, I appreciate that information, looks like this is going to be expensive. I will keep you posted when I get started.

[Author]

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